It has long been recognized that, in cold weather conditions, a significant amount of body heat is lost as a result of the inhalation of cold, dry air. This can result in discomfort in milder conditions and be a serious health hazard in arctic or sub-arctic conditions.
U.S. Pat. No. 5,706,802 granted Jun. 13, 1998 to McCormick discloses a cold weather breathing device with a heat exchanger module mounted in a cloth face mask. The heat exchanger module of this patent is of such design that it is very compact and light weight and yet has an elongated flow passage for the inflow and outflow of the breath of the user. The device provides high thermal efficiency in the transfer of heat to and from the breath of the user and yet it does not interpose a significant impedance to the flow of breath through the medium of the heat exchanger.
It is desirable to further improve the efficacy of the cold weather breathing device described above. It has been found that the coupling between the mouth of the user and the heat exchanger leaves something to be desired in respect to thermal efficiency and in respect to fitting of the mask to the user's face for eliminating dead air space, ease of breathing and comfort.
There are several prior art devices which address the problem of using the heat from exhaled air to warm inhaled air. For example, U.S. Pat. Nos. 4,458,679 granted Jun. 10, 1984 to Ward and 4,196,728 granted Apr. 8, 1980 to Granite disclose breathing devices including air inlet and outlet ports, a flow path therebetween, and a heat exchanging medium within the flow path for retaining the heat and humidity from exhaled air to warm and humidify inhaled air. Similarly, U.S. Pat. No. 4,150,671 granted Apr. 24, 1979 to Tiger discloses a mask including separate and concentric air inlet and outlet passages with heat exchanging fins surrounding the air inlet passage and disposed within the outlet passage for permitting the exchange of heat therebetween. U.S. Pat. No. 5,058,211 granted Oct. 22, 1991 to Hanks discloses a bandanna-type device to be wrapped around the face of a user including a strip of thermally insulative material retained within the bandanna and positioned adjacent the mouth of a user.
A general object of this invention to provide a combined face mask and heat exchanger with improved air flow and thermal coupling between the user's mouth and the heat exchanger and to overcome certain other disadvantages of the prior art.